Try this Candy Apples recipe, or contribute your own.
Reaching exactly 300 degrees Fahrenheit on a candy thermometer determines whether the sugar coating sets into a crisp, glassy shell or remains a sticky, chewy failure. Water, granulated sugar, and corn syrup undergo a precise transformation as moisture boils away, concentrating the sucrose molecules until they enter the hard-crack stage necessary for this confection. Commercial fruit often features a natural or applied wax barrier that prevents hot sugar syrup from adhering properly, which requires dipping the fruit into a hot vinegar solution beforehand to strip the surface clean.
Dry the apples completely after washing because any residual moisture will cause the boiling sugar to seize and slide off the skin. Twirl each fruit smoothly through the dyed syrup, letting excess liquid drip back into the pan to prevent thick pools from forming at the base during cooling. Selecting firm, tart varieties like Granny Smith provides a sharp flavor contrast against the intense sweetness of the hardened sugar shell.